The present invention relates to recognition/anti-collision lights and, more particularly, to a method and apparatus for extending the useful life of such lights and/or for detecting the failure of such lights.
Recognition/anti-collision lights are used on aircraft to produce bright flashes of light readily visible to the human eye for improving recognition of the aircraft from the ground or from other aircraft. The FAA (Federal Aviation Administration) currently mandates that aircraft have such lights with an acceptable minimum effective light intensity of 100 or 400 candela (depending on the aircraft) when viewed within five degrees of a horizontal plane.
Many prior art recognition/anti-collision lights include a flashtube, or strobe light, that initially produces a light intensity that meets government guidelines. However, the light intensity of the flashtube gradually degrades with use over time and eventually falls below the minimum intensity requirements, thereby requiring servicing and/or replacement of the flashtube. The mean time between failure (MTBF) of a typical flashtube is about 1500-3000 hours.
Anti-collision lights are therefore periodically tested, in some instances with elaborate equipment, to ensure that they meet the FAA requirements. A common practice has been to replace the lights on a scheduled basis to ensure proper illumination requirements are met even though many of the lights still satisfy illumination requirements.
In order to reduce the frequency at which a recognition/anti-collision light requires replacement, it would be desirable to have an anti-collision light with an improved (increased) mean time between failure (MTBF).
The present invention provides a recognition/anti-collision light including, in a preferred embodiment, two flashtubes and a control system that sequentially operates the two flashtubes in order to extend the overall useful life of the light. The invention also provides a technique for extending the life of a single flashtube or multiple flashtubes.
According to one aspect of the invention, a recognition light comprises a reflector having an axis and first and second annular semi-parabolic reflective surfaces which have respective focal points axially spaced apart from one another, and first and second annular lamps respectively disposed at the focal points.
According to another aspect of the invention, a recognition light comprises a parabolic reflector, first and second annular lamps surrounding the reflector, and a lens cover surrounding the reflector and lamps, the lens cover including a lens for focusing the light along a plane perpendicular to the axis of the reflector, the lens including first and second Fresnel lens portions each including a convex lens and a prism lens, the convex lenses being disposed adjacent one another and transaxially aligned with the first and second lamps, respectively.
According to another aspect of the invention, a recognition light comprises first and second lamps, a light detector positioned to detect light emitted from at least one of the lamps, a monitor circuit connected to the light detector for providing a fail signal when a characteristic of the light output of at least one of the lamps does not satisfy a specified criteria, and a control circuit connected to the monitor circuit and the first and second lamps for first activating the first lamp and then the second lamp in response to receipt of the fail signal of the monitor circuit.
According to another aspect of the invention, a recognition light of an aircraft comprises a flashtube, a light detector positioned to detect light emitted from the flashtube, a monitor circuit connected to the light detector for measuring the intensity of the detected light and comparing the measured intensity with a reference value corresponding to a predetermined light intensity level, and a control circuit connected to the flashtube and monitor circuit for flashing the flashtube at a first power level and then at an increased power level when the measured intensity drops below the reference value, thereby to increase the intensity of the flashes emitted by the flashtube to above the predetermined light intensity level.
According to another aspect of the invention, a method for increasing the useful life of a recognition light of an aircraft comprises flashing a flashtube, monitoring the light output of the flashtube, comparing the measured light output of the flashtube with a reference value corresponding to a predetermined light intensity value, increasing the power delivered to the flashtube when the measured light output drops below the reference value, thereby to increase the intensity of the flashes emitted by the flashtube to above the reference value.
According to a further aspect of the invention, a method for monitoring the useful life of an aircraft recognition light comprises flashing a flashtube, and monitoring the light output of the flashtube with a light detector that converts the detected light output into an integrated output voltage corresponding to the light output of a plurality of flashes of the flashtube.
According to another aspect of the invention, a method for increasing the useful life of a recognition light comprises providing first and second lamps, operating the first lamp, monitoring a characteristic of the light output of the first lamp and providing a fail signal when the characteristic of the light output of the first lamp does not satisfy a specified criteria, and stopping operation of the first lamp and operating the second lamp in response to receipt of the fail signal.
According to another aspect of the invention, a method for providing visual notification of required replacement of an anti-collision light prior to failure of the anti-collision light, comprises providing an anti-collision light including a lamp, operating the lamp at a first flash rate at a light intensity above a predetermined light intensity value, and operating the lamp at a second flash rate distinguishable from the first rate when the light intensity of the lamp approaches the predetermined light intensity value.
According to yet another aspect of the invention, a lamp fixture comprises an annular reflector and first and second annular lamps surrounding the reflector, and the reflector having a reflector surface configured to reflect light outwardly from the lamp fixture from both of the lamps.
The foregoing and other features of the invention are hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail one or more illustrative embodiments of the invention, such being indicative, however, of but one or a few of the various ways in which the principles of the invention may be employed.